This invention relates to dyes, to inks and to their use in ink jet printing (xe2x80x9cIJPxe2x80x9d). IJP is a non-impact printing technique in which droplets of ink are ejected through a fine nozzle onto a substrate without bringing the nozzle into contact with the substrate.
There are many demanding performance requirements for dyes and inks used in IJP. For example they desirably provide sharp, non-feathered images having good water-fastness, light-fastness and optical density. The inks are often required to dry quickly when applied to a substrate to prevent smudging, but they should not form a crust over the tip of an ink jet nozzle because this will stop the printer from working. The inks should also be stable to storage over time without decomposing or forming a precipitate which could block the fine nozzle.
According to the present invention there is provided a mono-azo compound of Formula (1) or a salt thereof: 
wherein:
A is N, Cxe2x80x94Cl, Cxe2x80x94CN or Cxe2x80x94NO2;
R1 is H or optionally substituted alkyl;
G is H, sulpho, carboxy, optionally substituted alkyl, optionally substituted alkoxy, xe2x80x94CF3, halo or xe2x80x94PO3H2;
L1 and L2 each independently is xe2x80x94SR2, xe2x80x94OR3 or xe2x80x94NR4R5;
R2, R3, R4 and R5 each independently is H, optionally substituted alkyl or optionally substituted aryl; or
R4 and R5 together with the nitrogen to which they are attached form an optionally substituted five or six membered ring;
provided that L1 and L2 are free from carboxy, sulpho and xe2x80x94PO3H2 groups.
The term mono-azo refers to compounds of Formula (1) with one azo group (xe2x80x94Nxe2x95x90Nxe2x80x94).
Preferably A is N.
R1 is preferably H or optionally substituted C1-4-alkyl, more preferably H or C1-4-alkyl optionally substituted by hydroxy, carboxy, sulpho or cyano. Examples include methyl, ethyl, n-propyl, iso-propyl, hydroxyethyl, cyanoethyl, sulphopropyl and carboxyethyl. It is especially preferred that R1 is H.
G is preferably attached ortho to the azo group. Preferably G is xe2x80x94SO3H, xe2x80x94COOH, xe2x80x94CF3, alkyl (preferably optionally substituted C1-4-alkyl), alkoxy (preferably optionally substituted C1-4-alkoxy) or xe2x80x94PO3H2, more preferably xe2x80x94SO3H, xe2x80x94COOH or xe2x80x94CF3 and especially xe2x80x94SO3H. Preferred optional substituents on G are selected from xe2x80x94OH, xe2x80x94SO3H, xe2x80x94COOH and xe2x80x94NH2.
When R2, R3, R4 or R5 is optionally substituted alkyl it is preferably optionally substituted C1-30-alkyl, The alkyl group may be straight-chain, branched-chain or cyclic (for example cyclohexyl). When it is a branched-chain alkyl, it is preferably an xcex1-branched alkyl group, for example xe2x80x94CH(CH3)CH2CH2CH3 or xe2x80x94CH(CH3)CH2CH(CH3)2. In one preferred embodiment the alkyl group is optionally substituted C1-10-alkyl, more preferably optionally substituted C1-6-alkyl and especially optionally substituted C1-4-alkyl. In a further preferred embodiment the alkyl group is optionally substituted C5-20-alkyl.
Preferred optional substituents on the alkyl groups represented by any of R2, R3, R4 or R5 include hydroxy, cyano, halo (especially F or Cl), nitro, C1-6-alkoxy, C1-6hydroxyalkoxy, a 5 or 6 membered heterocyclic group, or a group represented by T, wherein T is an optionally substituted amino group. Especially preferred substituents are selected from hydroxy, a 5 or 6 membered heterocyclic group and a group represented by T. Preferred 5 or 6 membered heterocyclic groups are optionally substituted furanyl and tetrahydrofuranyl, more preferably furanyl or tetrahydrofuranyl and especially furan-2-yl and tetrahydrofuran-2-yl.
Preferably T is a group of the formula xe2x80x94NR6R7 wherein R6 and R7 are each independently H, optionally substituted alkyl, xe2x80x94CO(alkyl), xe2x80x94CO(phenyl), or R6 and R7 together with the nitrogen to which they are attached form an optionally substituted morpholinyl, piperazinyl or piperidinyl ring.
When R6 or R7 is optionally substituted alkyl it is preferably optionally substituted C1-20-alkyl, more preferably optionally substituted C1-6alkyl, and especially C1-4-,alkyl, for example methyl, ethyl, n-propyl and iso-propyl. Preferred optional substituents on R6 and R7 are selected from xe2x80x94OH or xe2x80x94NH2.
When R6 or R7 is xe2x80x94CO(alkyl) it is preferably xe2x80x94CO(C1-6-alkyl), more preferably xe2x80x94CO(C1-4-alkyl). For example xe2x80x94COCH2CH3 and xe2x80x94COCH2CH2CH3.
When R6 and R7 together with the nitrogen to which they are attached form a substituted morpholinyl, piperidinyl or piperazinyl ring it is preferably substituted by C1-4-alkyl, C1-4-hydroxyalkyl, xe2x80x94CO(C1-4-alkyl) or a group of the formula xe2x80x94Mxe2x80x94NR8R9 wherein M is an alkylene linking group and R8 and R9 each independently is H or C1-6-alkyl optionally substituted by hydroxy or C1-6-alkoxy. M is preferably C1-6-alkylene, more preferably C2-6-alkylene and especially xe2x80x94(CH2)gxe2x80x94, wherein g is from 2 to 6.
Further preferred groups represented by T include xe2x80x94NH2; xe2x80x94NH(C1-30(-alkyl), for example ethylamino, xe2x80x94NHCH(CH)3CH2CH3 and xe2x80x94NHC16H33; xe2x80x94N(C1-6-alkyl)2, for example di-ethylamino; xe2x80x94NHCO(C1-4-alkyl), for example xe2x80x94NHCOCH3 and xe2x80x94NHCOCH2CH3; xe2x80x94NH(Phenyl); morpholinyl; piperazinyl; and substituted piperazinyl groups of the Formula (2): 
wherein:
Y is C1-4-alkyl, C1-4-hydroxyalkyl, xe2x80x94CO(C1-4-alkyl) or a group of the formula xe2x80x94Mxe2x80x94NR8R9; and
M, R8 and R9 are as hereinbefore defined.
Preferred groups of the Formula (2) include for example: 
A preferred alkyl group substituted by T which may be represented by any of R2, R3, R4 and R5 is of the formula xe2x80x94(CdH2d)xe2x80x94T wherein d is 1 to 6, more preferably 2 to 6 and T is as hereinbefore defined.
A further preferred optionally substituted alkyl group represented by any of R2, R3, R4 and R5 is of the Formula (3):
xe2x80x94(CaH2aO)t(CbH2bO)qR10xe2x80x83xe2x80x83Formula (3)
wherein:
R10 is H or alkyl optionally substituted by xe2x80x94NH2;
a and b are different and from 1 to 6;
t is from 1 to 4; and
q is from 0 to 3.
Preferably R10 is H or C1-4-alkyl, more preferably H.
Preferably a and b are each independently 2 to 6, more preferably 2 or 3, t is 1 or 2 and q is 0.
Preferred groups of Formula (3) include xe2x80x94(C2-6-alkylene)O(C2-6-alkylene)OC1-4alkyl, for example xe2x80x94C2H4OC2H4OCH3, and xe2x80x94(C2-6-alkylene)O(C2-6-alkylene)OH, for example xe2x80x94C2H4OC2H4OH, xe2x80x94CH2CH(CH3)CH2OC2H4OH and xe2x80x94C3H6OC2H4OH.
When R2, R3, R4 or R5 is optionally substituted aryl it is preferably optionally substituted phenyl or optionally substituted naphthyl, more preferably a group of the Formula (4) or (5): 
wherein:
each R11 independently is C1-6-alkoxy, C1-6-hydroxyalkoxy, hydroxy, halo (preferably F or Cl), nitro, amino, xe2x80x94COC1-6-alkyl, xe2x80x94NHCOC1-6-alkyl or xe2x80x94NHC1-6-hydroxyalkyl;
each Q independently is optionally substituted C1-30-alkyl or a group of the Formula xe2x80x94Zxe2x80x94Q1;
each Z independently is a divalent linking group;
each Q1 independently is optionally substituted C1-30-alkyl;
n and m each independently is 0 to 5; and
(n+m)=0 to 5.
m is preferably 0, 1 or 2, more preferably 1 or 2.
n is preferably 0 or 1.
(n+m) is preferably 1 to 3 more preferably 1 or 2.
Each Z is preferably independently selected from xe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94, xe2x80x94NRaxe2x80x94, xe2x80x94SO2xe2x80x94 and xe2x80x94SO2NRaxe2x80x94, wherein Ra is H or C30-alkyl optionally substituted by a group other than xe2x80x94COOH, xe2x80x94SO3H or xe2x80x94PO3H2. Preferably Ra is H or C1-20-alkyl, more preferably H or C1-6-alkyl and especially H.
Q and Q1 may be a straight chain or branched chain alkyl group. When any of Q or Q1 is a branched chain alkyl group it is preferably branched at the xcex1-carbon. In a preferred embodiment Q and Q1 are each independently C1-4-alkyl. In a further preferred embodiment Q and Q1 are each independently optionally substituted C5-20-alkyl.
When any of Q or Q1 is substituted, the substituents are preferably selected from hydroxy, cyano, halo (especially F or Cl), nitro, C1-6-alkoxy, C1-6-hydroxyalkoxy, a 5 or 6 membered heterocyclic group, or a group represented by T, wherein T is as hereinbefore defined. It is preferred, however, that Q and Q1 are unsubstituted.
Preferably R4 and R5 are not both optionally substituted aryl.
When R4 and R5 together with the nitrogen to which they are attached form an optionally substituted 5 or 6 membered ring it is preferably a morpholinyl or an optionally substituted piperazinyl ring. The substituents are preferably selected from hydroxy, halo, C1-6-alkoxy, C1-6-alkyl and C1-6-alkyl substituted by hydroxy or a group represented by T as hereinbefore defined. More preferably the substituents are selected from C1-6-alkyl or a group of the formula xe2x80x94C1-6-alkylene-T. When R4 and R5 together with the nitrogen to which they are attached form a substituted piperazinyl ring it is preferably substituted on a nitrogen atom.
It is especially preferred that when R4 and R5 together with the nitrogen to which they are attached form a 5 or 6 membered ring it is morpholinyl, piperazinyl or piperidinyl optionally substituted by C1-4-alkyl or C1-4-hydroxyalkyl.
R2, R3, R4 and R5 are preferably free from sulphatoethylsulphonyl and vinylsulphone groups.
It is preferred that R2, R3, R4 and R5 are each independently H, C,1-30-alkyl optionally substituted by hydroxy, a 5 or 6 membered heterocyclic group or a group represented by T, or R4 and R5 together with the nitrogen to which they are attached form an optionally substituted morpholinyl, piperidinyl or piperazinyl ring.
Preferred groups of the formula xe2x80x94NR4R5 include xe2x80x94NHR5, morpholinyl, piperidinyl or piperazinyl optionally substituted by C1-6-alkyl or a group of the formula xe2x80x94(C1-6-alkylene)xe2x80x94T wherein T and R5 are as hereinbefore defined.
When L1 and/or L2 is a group of the formula xe2x80x94NHR5 it is preferably of the formulaxe2x80x94NHRb, wherein Rb is xe2x80x94(C1-6-alkylene)O(C1-6-alkylene)OR10; a group of the Formula (4); or C1-30-alkyl optionally substituted by one or more of furanyl, tetrahydrofuranyl, xe2x80x94OH or T wherein T, R10 and Formula (4) are as hereinbefore defined. Preferably Rb is C1-30-alkyl optionally substituted by one or more of xe2x80x94OH, furanyl, tetrahydrofuranyl or T wherein T is as hereinbefore defined. It is especially preferred that Rb is C1-6-alkyl optionally substituted by two to five xe2x80x94OH groups. A further preferred group of the formula xe2x80x94NHRb is of the formula xe2x80x94NH(CdH2d)xe2x80x94T wherein d is 1 to 6
Examples of preferred groups of the formula xe2x80x94NHRb which may be represented by L1 and L2 include: 
A first preferred embodiment of the present invention comprises a compound of the Formula (6) or a salt thereof: 
wherein:
X1 and X2 each independently is xe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94or xe2x80x94NR12xe2x80x94;
W1 and W2 each independently is H, a group T, xe2x80x94O(C1-6-alkylene)OR10, C1-6-alkoxy, hydroxy or a 5 or 6 membered heterocyclic group;
R12 is H or C1-20-alkyl (preferably C1-6-alkyl) optionally substituted by hydroxy, C1-4-alkoxy or a group T;
p and q are each independently 1 to 20; or
xe2x80x94X1xe2x80x94(CpH2p)W1 and xe2x80x94X2xe2x80x94(CqH2q)W2 each independently form a piperazinyl, morpholinyl or piperidinyl ring; and
T, R1 and R10 are as hereinbefore defined;
provided that W1, W2 and R12 are free from carboxy, sulpho and xe2x80x94-PO3H2 groups.
In one embodiment p and q each independently is 1 to 4 and in a second embodiment p and q each independently is from 5 to 20.
The compounds of Formula (6) provide prints which exhibit a high light-fastness when incorporated into inks for ink jet printing. The compounds of Formula (6) are also highly soluble which improves operability and reduces crusting when inks containing the compounds are used in an ink jet printer.
When W1 or W2 is a 5 or 6 membered heterocyclic group it is preferably piperazinyl, morpholinyl, furanyl or tetrahydrofuranyl, more preferably it is morpholinyl, piperazinyl, furan-2-yl, or tetrahydrofuran-2-yl of the formula: 
R12 is preferably H or C1-4-alkyl optionally substituted by hydroxy. It is especially preferred that R12 is H.
A second preferred embodiment of the present invention comprises a compound of Formula (6) and salts thereof wherein
X1 and X2 each independently is xe2x80x94NR12xe2x80x94(preferably xe2x80x94NHxe2x80x94); and
W1, W2, R1, R12, p and q are as hereinbefore defined;
provided that W1, W2 and R12 are free from carboxy, sulpho and xe2x80x94PO3H2 groups.
A third preferred embodiment of the present invention comprises a compound of Formula (6) or a salt thereof wherein:
W1 and W2 each independently is H, xe2x80x94OC1-6-alkylenexe2x80x94OR10, C1-6-alkoxy, xe2x80x94NH2, xe2x80x94NR3CO(C1-4-alkyl), hydroxy, morpholinyl or tetrahydrofuranyl;
R13 is H or C1-4-alkyl; and
X1, X2, R1, R10, R12, p and q are as hereinbefore defined.
A fourth preferred embodiment of the present invention comprises a compound of the Formula (7) or a salt thereof: 
wherein:
R1, X1, X2, W1, Q, m and p are as hereinbefore defined;
provided that W1, X1, X2 and each Q are free from carboxy, sulpho and xe2x80x94PO3H2 groups.
Especially preferred compounds of the Formula (7) are those wherein R1 is H or C1-4-alkyl; X1 and X2 each independently is xe2x80x94Sxe2x80x94 or xe2x80x94NR12xe2x80x94 (more preferably xe2x80x94NHxe2x80x94), wherein R12 is as hereinbefore defined; W1 is H, tetrahydrofuranyl or xe2x80x94OH; each Q independently is
C1-20-alkyl (more preferably C5-20-alkyl); m is 0, 1 or 2; and p is 1-20 (more preferably 5 to 20).
Further preferred compounds of Formula (7) are those wherein each Q independently is C1-4-alkyl.
A fifth preferred embodiment of the present invention comprises compounds of the Formula (1) and salts thereof wherein G is xe2x80x94SO3H and is attached ortho to the azo group; L1 and L2 each independently is xe2x80x94NHRb wherein Rb is as hereinbefore defined; and R1 is H or C1-4-alkyl. In a further embodiment L1 and/or L2 contains an xcex1-branched alkyl group.
The compounds of the invention may be in the free acid or salt form. Preferred salts are water-soluble, for example alkali metal salts, especially lithium, sodium and potassium salts, ammonium and substituted ammonium salts. Especially preferred alkali metal salts are those with sodium and lithium.
Especially preferred ammonium and substituted ammonium salts have cations of the formula *NV4 wherein each V independently is H or optionally substituted alkyl, or two groups represented by V are H or optionally substituted alkyl and the remaining two groups represented by V, together with the N atom to which they are attached, form a 5- or 6-membered ring (preferably a morpholinyl, pyridinyl or piperidinyl ring).
Preferably each V independently is H or C1-4-alkyl, more preferably H, CH3 or CH3CH2, especially H. Thus the cation is preferably ammonium (i.e.+NH4).
Examples of cations include +NH4, morpholinium, piperidinium, pyridinium, (CH3)3N+H, (CH3)2N+H2, H2N+(CH3)(CH2CH3),CH3N+H3, CH3CH2N+H3, H2N+(CH2CH3)2, CH3CH2CH2N+H3, CH3CH2CH2N+H3, (CH3)2CHN+H3, N+(CH3)4, N+(CH2CH3)4, N-methyl pyridinium, N,N-dimethyl piperidinium and N,N-dimethyl morpholinium.
The compounds may be converted into a salt using known techniques. For example, an alkali metal salt of a dye may be converted into a salt with ammonia or an amine by dissolving an alkali metal salt of the dye in water, acidifying with a mineral acid and adjusting the pH of the solution to pH 9 to 9.5 with ammonia or the amine and removing the alkali metal cations by dialysis.
The present invention covers all tautomeric forms of the compounds shown in this specification, for example the hydrazo tautomers.
The present invention also covers mixtures comprising one or more compounds of the Formula (1); and mixtures comprising one or more compounds of the Formula (1) and one or more water-soluble dye (preferably a magenta dye) other than a compound of Formula (1). For example a mixture comprising a compound of Formula (1) and one or more water-soluble magenta dye selected from a xanthene dye, an azo dye and a bis azo dye.
The compounds of the invention may be prepared using conventional techniques for the preparation of azo dyes. For example a suitable method comprises condensing a compound of the Formula (8) with a compound of the Formula L2H: 
wherein A, R1, G, L1 and L2 are as hereinbefore defined.
The condensation is preferably performed in a liquid medium, more preferably an aqueous medium and especially water. Temperatures of 15xc2x0 C. to 100xc2x0 C. are preferred, more preferably from 60 to 70xc2x0 C. Preferably a reaction time of 1 to 48, more preferably 3 to 24 hours is used.
The condensation is preferably performed in the presence of a base. The base may be any inorganic base for example, ammonia, an alkali metal or alkali earth metal hydroxide, carbonate or bicarbonate, or an organic base. Preferred organic bases are tertiary amines for example, N-alkylated heterocycles, for example N-(C1-4-alkyl)morpholine, N-(C1-4-alkyl)piperidine, N,Nxe2x80x2-di(C1-4-alkyl)piperazine; tri(C1-4-alkyl)amines, for example triethylamine, and optionally substituted pyridines, especially pyridine.
The amount of base used may be varied between wide limits but it is preferred to use less than 40, more preferably less than 10 and especially from 3 to 5 moles for each mole of the compound of Formula (8).
After the condensation the product may be isolated by precipitating the product as a salt from the reaction mixture for example by the addition of a suitable alkali metal salt, especially sodium chloride. Alternatively, the product may be isolated in its free acid form by acidifying the reaction mixture, preferably using a mineral acid, especially hydrochloric acid. Where the product precipitates as a solid it may be separated from the mixture by filtration.
If desired unwanted anions may be removed from the product of the above process by dialysis, osmosis, ultrafiltration or a combination thereof.
The product of the above process may be converted, if desired, to the NH4+, quaternary ammonium or organic amine salt by the addition of ammonia, ammonium hydroxide, primary, secondary, tertiary or quaternary amine. When the base used in the condensation process is an organic amine an excess may be used so that the compound of Formula (1) is formed as the organic amine salt.
The compound of the Formula (8) may be prepared using conventional techniques, for example by:
(1) diazotising the compound of the formula: 
wherein G is as hereinbefore defined, to give the corresponding diazonium salt;
(2) coupling the diazonium salt from stage (1) with 2-amino-8-naphthol-3,6-disulphonic acid at a pH less than 7, preferably at a pH of from 3 to 5;
(3) alkaline hydrolysis of the product of stage (2) to remove the acetyl group;
(4) condensing the product from stage (1) with a compound of the formula: 
wherein A is as hereinbefore defined; and
(5) condensing the product from stage (4) with approximately 1 molar equivalent of the compound of the formula L1H.
The diazotisation in stage (1) is preferably performed in an aqueous medium at a pH below 7 in the presence of a suitable diazotisation agent. Dilute mineral acid, e.g. HCl or H2SO4, is preferably used to achieve the desired acidic conditions. Conveniently the diazotisation agent is formed in-situ, for example by dissolving an alkali metal nitrite, preferably sodium nitrite, in a molar excess of mineral acid, preferably HCl. Normally at least one mole of diazotisation agent per mole of the amine in stage (1) preferably from 1 to 1.25 moles will be used in the diazotisation.
The temperature of the diazotisation is not critical and may conveniently be carried out at from xe2x88x925xc2x0 C. to 20xc2x0 C., preferably from 0 to 10xc2x0 C. and especially from 0 to 5xc2x0 C.
The hydrolysis in stage (3) is preferably performed at a pH in the range 9 to 14.
The temperature during hydrolysis is preferably from 40 to 90xc2x0 C.
The compounds of Formula (1) are useful as dyes, especially for the coloration of inks for ink jet printing.
According to a second aspect of the present invention there is provided an ink comprising:
(a) from 0.01 to 30 parts of a compound of the Formula (9); and
(b) from 70 to 99.99 parts of a medium comprising (i), (ii) or (iii):
(i) a mixture of water and an organic solvent;
(ii) an organic solvent free from water; or
(iii) a low melting point solid;
wherein all parts are by weight and the number of parts of (a)+(b)=100: 
wherein:
L3 is L1 or a labile atom or group;
L4 is L2 or a labile atom or group;
A, R1, G, L1 and L2 are as hereinbefore defined;
provided that L3 and L4 are free from carboxy, sulpho and xe2x80x94PO3H2 groups.
When L3 or L4 is a labile atom or group, it is preferably an atom or group which is bound by a chemical bond to the compound of Formula (9) which is displaceable by a hydroxyl group of cellulose under mildly alkaline aqueous conditions to form a covalent bond between the compound of Formula (9) and cellulose.
Preferred labile atoms and groups represented by L3 and L4 include halogen atoms, for example F and Cl; thiocyano groups; quaternary ammonium groups, for example trialkylammonium groups and optionally substituted pyridinium groups.
Preferably L3 is L1 and L4 is L2 as hereinbefore defined for the first aspect of the invention.
In the inks according to the second aspect of the present invention the compound of Formula (9) is preferably of Formula (1), more preferably of Formula (6) or (7) as hereinbefore defined.
The number of parts of component (a) is preferably from 0.1 to 20, more preferably from 0.5 to 15, and especially from 1 to 5 parts. The number of parts of component (b) is preferably from 99.9 to 80, more preferably from 99.5 to 85, especially from 99 to 95 parts.
When the medium is a mixture of water and an organic solvent or an organic solvent free from water, preferably component (a) is completely dissolved in component (b). Preferably component (a) has a solubility in component (b) at 20xc2x0 C. of at least 10%. This allows the preparation of concentrates which may be used to prepare more dilute inks and reduces the chance of the dye precipitating if evaporation of the liquid medium occurs during storage.
When the medium comprises a mixture of water and an organic solvent, the weight ratio of water to organic solvent is preferably from 99:1 to 1:99, more preferably from 99:1 to 50:50 and especially from 95:5 to 80:20.
It is preferred that the organic solvent present in the mixture of water and organic solvent is a water-miscible organic solvent or a mixture of such solvents. Preferred water-miscible organic solvents include C1-6-alkanols, preferably methanol, ethanol, n-propanol, isopropanol, n-butanol, sec-butanol, tert-butanol, n-pentanol, cyclopentanol and cyclohexanol; linear amides, preferably dimethylformamide or dimethylacetamide; ketones and ketone-alcohols, preferably acetone, methyl ether ketone, cyclohexanone and diacetone alcohol; water-miscible ethers, preferably tetrahydrofuran and dioxane; diols, preferably diols having from 2 to 12 carbon atoms, for example pentane-1,5-diol, ethylene glycol, propylene glycol, butylene glycol, pentylene glycol, hexylene glycol and thiodiglycol and oligo- and poly-alkyleneglycols, preferably diethylene glycol, triethylene glycol, polyethylene glycol and polypropylene glycol; triols, preferably glycerol and 1,2,6-hexanetriol; mono-C1-4-alkyl ethers of diols, preferably mono-C1-4-alkyl ethers of diols having 2 to 12 carbon atoms, especially 2-methoxyethanol, 2-(2-methoxyethoxy)ethanol, 2-(2-ethoxyethoxy)-ethanol, 2-[2-(2-methoxyethoxy)ethoxy]ethanol, 2-[2-(2-ethoxyethoxy)-ethoxy]-ethanol and ethyleneglycol monoallylether; cyclic amides, preferably 2-pyrrolidone, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, caprolactam and 1,3-dimethylimidazolidone; cyclic esters, preferably caprolactone; sulphoxides, preferably dimethyl sulphoxide and sulpholane. Preferably the liquid medium comprises water and 2 or more, especially from 2 to 8, water-soluble organic solvents.
Especially preferred water-soluble organic solvents are cyclic amides, especially 2-pyrrolidone, N-methyl-pyrrolidone and N-ethyl-pyrrolidone; diols, especially 1,5-pentane diol, ethyleneglycol, thiodiglycol, diethyleneglycol and triethyleneglycol; and mono-C1-4-alkyl and C1-4-alkyl ethers of diols, more preferably mono-C1-4-alkyl ethers of diols having 2 to 12 carbon atoms, especially 2-methoxy-2-ethoxy-2-ethoxyethanol.
A preferred medium comprises:
(a) from 75 to 95 parts water; and
(b) from 25 to 5 parts in total of one or more solvents selected from diethylene glycol, 2-pyrrolidone, thiodiglycol, N-methylpyrrolidone, cyclohexanol, caprolactone, caprolactam and pentane-1,5-diol;
wherein the parts are by weight and the sum of the parts (a) and (b)=100.
Examples of further suitable ink media comprising a mixture of water and one or more organic solvents are described in U.S. Pat. Nos. 4,963,189, 4,703,113, 4,626,284 and EP 4,251,50A.
When the liquid medium comprises an organic solvent free from water, (i.e. less than 1% water by weight) the solvent preferably has a boiling point of from 30xc2x0 to 200xc2x0 C., more preferably of from 40xc2x0 to 150xc2x0 C., especially from 50 to 125xc2x0 C. The organic solvent may be water-immiscible, water-miscible or a mixture of such solvents. Preferred water-miscible organic solvents are any of the hereinbefore described water-miscible organic solvents and mixtures thereof. Preferred water-immiscible solvents include, for example, aliphatic hydrocarbons; esters, preferably ethyl acetate; chlorinated hydrocarbons, preferably CH2Cl2; and ethers, preferably diethyl ether; and mixtures thereof.
When the liquid medium comprises a water-immiscible organic solvent, preferably a polar solvent is included because this enhances solubility of the dye in the liquid medium. Examples of polar solvents include C1-4-alcohols. In view of the foregoing preferences it is especially preferred that where the liquid medium is an organic solvent free from water it comprises a ketone (especially methyl ethyl ketone) and/or an alcohol (especially a C1-4-alkanol, more especially ethanol or propanol).
The organic solvent free from water may be a single organic solvent or a mixture of two or more organic solvents. It is preferred that when the medium is an organic solvent free from water it is a mixture of 2 to 5 different organic solvents. This allows a medium to be selected which gives good control over the drying characteristics and storage stability of the ink.
Ink media comprising an organic solvent free from water are particularly useful where fast drying times are required and particularly when printing onto hydrophobic and non-absorbent substrates, for example plastics, metal and glass.
Preferred low melting solid media have a melting point in the range from 60xc2x0 C. to 125xc2x0 C. Suitable low melting point solids include long chain fatty acids or alcohols, preferably those with C18-24 chains, and sulphonamides. The dye of Formula (9) may be dissolved in the low melting point solid or may be finely dispersed in it.
The compounds according to the present invention exhibit a high solubility in aqueous media, accordingly it is preferred that the liquid medium is a mixture of water and one or more water miscible organic solvent(s).
The ink may also contain additional components conventionally used in ink jet printing inks, for example viscosity and surface tension modifiers, corrosion inhibitors, biocides, kogation reducing additives and surfactants which may be ionic or non-ionic.
The presence of impurities in an ink jet printing ink can result in the formation of precipitates in the ink. This is undesirable because the precipitates can block the narrow ink jet nozzle in the printer. Therefore, the compounds(s) according to the first aspect of the present invention may be, and preferably are, purified to remove undesirable impurities before they are incorporated into inks for ink jet printing. Conventional techniques may be employed for purifying the compounds, for example osmosis and/or dialysis.
A third aspect of the present invention provides a process for printing an image on a substrate comprising applying thereto an ink containing a compound of Formula (9) as hereinbefore defined by means of an ink jet printer.
The Preferred ink used in this process is an ink according to the second aspect of the present invention.
The ink jet printer preferably applies the ink to the substrate in the form of droplets which are ejected through a small orifice onto the substrate. Preferred ink jet printers are piezoelectric ink jet printers and thermal ink jet printers. In thermal ink jet printers, programmed pulses of heat are applied to the ink in a reservoir by means of a resistor adjacent to the orifice, thereby causing the ink to be ejected in the form of small droplets directed towards the substrate during relative movement between the substrate and the orifice. In piezoelectric ink jet printers the oscillation of a small crystal causes ejection of the ink from the orifice.
The substrate is preferably paper, plastic, a textile, metal or glass, more preferably paper, an overhead projector slide or a textile material, especially paper.
Preferred papers are plain or treated papers which may have an acid, alkaline or neutral character. Examples of commercially available papers include, HP Premium Coated Paper, HP Photopaper (all available from Hewlett Packard Inc), Stylus Pro 720 dpi Coated Paper, Epson Photo Quality Glossy Film, Epson Photo Quality Glossy Paper (available from Seiko Epson Corp.), Canon HR 101 High Resolution Paper, Canon GP 201 Glossy Paper, Canon HG 101 High Gloss Film (all available from Canon Inc.), Wiggins Conqueror paper (available from Wiggins Teape Ltd), Xerox Acid Paper and Xerox Alkaline paper.
A fourth aspect of the present invention provides a paper, an overhead projector slide or a textile material printed with an ink according to the second aspect of the present invention, or by means of the process according to the third aspect of the present invention.
When the substrate is a textile material the ink according to the invention is preferably applied thereto by:
i) applying the composition to the textile material using an ink jet printer; and
ii) heating the printed textile material at a temperature of from 50xc2x0 C. to 250xc2x0 C.
Preferred textile materials are natural, synthetic and semi-synthetic materials. Examples of preferred natural textile materials include wool, silk, hair and cellulosic materials, particularly cotton, jute, hemp, flax and linen. Examples of preferred synthetic and semi-synthetic materials include polyamides, polyesters, polyacrylonitriles and polyurethanes.
Preferably the textile material has been treated with an aqueous pretreatment composition comprising a thickening agent and optionally a water-soluble base and a hydrotropic agent and dried prior to step i) above.
The pre-treatment composition preferably comprises a solution of the base and the hydrotropic agent in water containing the thickening agent. Particularly preferred pre-treatment compositions are described more fully in EP-A-534 660.
A fifth aspect of the present invention provides an ink jet cartridge containing an ink, wherein the ink contains a compound of the Formula (9) as hereinbefore defined in relation to the second aspect of the present invention.
Preferably the ink jet cartridge contains an ink according to the second aspect of the invention.